Link insertion now loads clipboard URLs when available.
The 'Insert Link' alert dialog now has a clear button.
Added the title field to inserting and updating links.
Improved the documentation for the new parsing methods.
The link title can now be editted too.
Links can be removed from the update alert dialog.
Rolled back some test changes.  Link fields are also no longer marked required, since we currently have no mechanism to prevent the user from leaving them blank.
Replaces several NSAssert() with NSParameterAssert().
URLs in the clipboard are now validated before pasting them in the link insertion dialogue.
Editing the link title on insertion now works. An empty title means the URL will be used instead.
Inserting a link without a title works now.
Merge pull request #179 from wordpress-mobile/169-linkImprovements

Linking improvements.